Carboxy-functional, polyether-based reaction products and aqueous basecoat materials comprising the reaction products

ABSTRACT

R is a C3 to C6 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 800 to 4000 g/mol, the components (a) and (b) being used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and the resulting reaction product possessing an acid number of 10 to 50 mg KOH/g.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of prior U.S. applicationSer. No. 16/060,482, filed Jun. 8, 2018, the disclosure of which isincorporated herein by reference in its entirety. U.S. application Ser.No. 16/060,482 is the nation stage of PCT/EP2016/079192, filed Nov. 30,2016, the disclosure of which is incorporated herein by reference in itsentirety. U.S. application Ser. No. 16/060,482 calims priority toEuropean Patent Application No. 15198679.1, filed Dec. 9, 2015, thedisclosure of which is incorporated herein by reference in its entirety.

The present invention relates to innovative carboxy-functional,polyether-based reaction products. It further relates to aqueousbasecoat materials which comprise the reaction products and also to theuse of said reaction products in aqueous basecoat materials. Itadditionally relates to a method for producing multicoat paint systemsusing aqueous basecoat materials, and also to the multicoat paintsystems producible by means of said method.

Prior Art

There are a multiplicity of known methods for producing multicoat colorand/or effect paint systems (also called multicoat finishes). The priorart (compare, for example, German patent application DE 199 48 004 A1,page 17, line 37, to page 19, line 22, or German patent DE 100 43 405C1, column 3, paragraph [0018], and column 8, paragraph [0052], column9, paragraph [0057], in conjunction with column 6, paragraph [0039], tocolumn 8, paragraph [0050]), for example, discloses the followingmethod, which involves

-   (1) applying a pigmented aqueous basecoat material to a substrate,-   (2) forming a polymer film from the coating material applied in    stage (1),-   (3) applying a clearcoat material to the resultant basecoat, and    subsequently-   (4) curing the basecoat together with the clearcoat.

This method is widely used, for example, for the original finish (OEM)of automobiles and also for the painting of metal and plastic parts forinstallation in or on vehicles. The present-day requirements for thetechnological qualities of such paint systems (coatings) in applicationare massive.

A constantly recurring problem and one still not resolved to entiresatisfaction by the prior art is the incidence of adhesion problems inthe case of the multicoat systems produced. Particularly in relation tothe adhesion between basecoat and the coating beneath it as viewed fromthe substrate, and also to the adhesion between basecoat and clearcoat,problems occur very frequently. The problematic adhesion is especiallystriking when the coated substrates are exposed to weathering. In thecase of exposure through weathering, poor adhesion is also manifestedparticularly in the incidence of blisters and swelling. Particularly inconnection with refinishing, problems may arise here. A likewiseconstantly recurring problem is the often inadequate mechanicalstability, particularly with respect to stonechip effects.

The qualities of the basecoat material, which is particularly importantin this context, and of the coats produced from it are determined inparticular by the binders and additives—for example, specific reactionproducts—present in the basecoat material.

A further factor is that nowadays the replacement of coatingcompositions based on organic solvents by aqueous coating compositionsis becoming ever more important, in order to meet the risingrequirements for environmental compatibility.

EP 1 454 971 B1 discloses polyester polyols which are obtainable byreaction of at least one polycarboxylic acid and at least one OHcompound. At least 45 mol % of the polycarboxylic acid used hereconsists of trimellitic anhydride. The OH compound has an averagemolecular weight of at least 210 g/mol and preferably an averagemolecular weight of not more than 650 g/mol. Particularly preferred foruse is polytetrahydrofuran having a number-average molecular weight of250 g/mol as OH compound. The polyester polyol finds application forimproving the technological and particularly the esthetic qualities ofmulticoat paint systems, and is used in basecoat materials.

Problem

The problem addressed by the present invention was therefore that ofproviding a reaction product which can be used to produce coatings thatno longer have the disadvantages referred to above in the prior art.More particularly, the provision of a new reaction product and the usethereof in aqueous basecoat materials ought to create the opportunityfor provision of coatings which exhibit outstanding adhesion qualitiesand very good stonechip resistance and which at the same time can beproduced in an eco-friendly way through the use precisely of aqueousbasecoat materials.

Solution

The problems stated have been solved by a pigmented aqueous basecoatmaterial which comprises a carboxy-functional, polyether-based reactionproduct which is preparable by reaction of

(a) at least one carboxylic anhydride comprising a free carboxylic acidgroup and/or the halide of a carboxylic acid group with

(b) at least one polyether of the general structural formula (I)

in which

R is a C₃ to C₆ alkylene radical and n is selected accordingly such thatthe polyether (b) possesses a number-average molecular weight of 800 to4000 g/mol,

the components (a) and (b) being used in the reaction in a molar ratioof 0.7/2.3 to 1.6/1.7 and the resulting reaction product possessing anacid number of 5 to 50 mg KOH/g.

The condition that n is selected such that said polyether possesses anumber-average molecular weight of 800 to 4000 g/mol may be illustratedas follows: Where, for example, R is a tetramethylene radical and thenumber-average molecular weight is to be 1000 g/mol, n is on averagebetween 13 and 14. From the mandates given, the skilled person is wellaware of how to produce or select a corresponding reaction product.Apart from this, the description below, and particularly the examples,further provide additional information. The parameter n is therefore tobe understood as a statistical average value, just like thenumber-average molecular weight.

The new basecoat material is also referred to below as basecoat materialof the invention. Preferred embodiments of the basecoat material of theinvention are apparent from the following description and also from thedependent claims.

Likewise provided for the present invention is the reaction product perse and also the use of the reaction product in aqueous basecoatmaterials for improving the adhesion qualities and stonechip resistance.The present invention relates not least to a method for producing amulticoat paint system on a substrate and also to a multicoat systemproduced by the stated method.

Through the use of the reaction products of the invention, basecoatmaterials are obtained whose use in the context of production ofcoatings, especially multicoat paint systems, leads to outstandingadhesion qualities and very good stonechip resistance. The reactionproduct of the invention and also the basecoat material of the inventioncan be used in the area of original finishing, particularly in theautomobile industry sector, and in the area of automotive refinish.

Component (a)

The reaction product of the invention is preparable using at least onecyclic carboxylic anhydride comprising a free carboxylic acid group(-COOH) and/or the halide, preferably chloride (-COCl), of a carboxylicacid group. Preference is given to a free carboxylic acid group (COOH).

Component (a) may comprise aliphatic, aromatic, or araliphatic (mixedaliphatic-aromatic) cyclic carboxylic anhydrides which comprise a freecarboxylic acid group. Cyclic carboxylic anhydrides are understood asthose in which the anhydride group is present in a ring structure. Thisis therefore synonymous with saying that on reaction of the anhydridegroup and on corresponding opening of the anhydride function, as forexample on reaction with a hydroxyl group and corresponding formation ofa free carboxylic acid group and an ester group, the parent moleculedoes not break apart into two molecules, but instead that there is onlyone molecule even after the reaction.

Preferred aromatic carboxylic anhydrides are those which comprise a freecarboxylic acid group. These are therefore compounds which apart fromthe free carboxylic acid group and the anhydride group consist solely ofaromatic structural units. Especially preferred is trimelliticanhydride.

Component (b)

The reaction products of the invention may be prepared using at leastone polyether of the general structural formula (I)

where R is a C₃ to C₆ alkyl radical. The index n should be selected ineach case such that said polyether possesses a number-average molecularweight of 800 to 4000 g/mol. With preference it possesses anumber-average molecular weight of 950 to 3800 g/mol, more preferably of1050 to 3600 g/mol, more particularly of 1200 to 3400 g/mol, and verypreferably 1500 to 3200 g/mol. Further preferred is a range from 1600 to3000 g/mol, more particularly 1800 to 2200 g/mol. The number-averagemolecular weight may for example be 1000 g/mol, 2000 g/mol, or 3000g/mol.

For the purposes of the present invention, unless specifically indicatedotherwise, the number-average molecular weight is determined by means ofvapor pressure osmosis. Measurement for the purposes of the presentinvention was carried out by means of a vapor pressure osmometer (model10.00 from Knauer) on concentration series of the component underanalysis in toluene at 50° C. with benzophenone as calibration substanceto determine the experimental calibration constant of the instrumentused (according to E. Schröder, G. Müller, K.-F. Arndt, “Leitfaden derPolymercharakterisierung” [Principles of polymer characterization],Akademie-Verlag, Berlin, pp. 47-54, 1982, where the calibrationsubstance used was benzil).

As is known, and as has already been elucidated earlier on above, thenumber-average molecular weight is always a statistical average value.The same must therefore also be true of the parameter n in formula (I).The designation “polyether” selected for component (b), and requiringelucidation in this context, is understood as follows: for polymers,polyethers (b) for example, the compounds are always mixtures ofmolecules with different sizes. At least some or all of these moleculesare distinguished by a sequence of identical or different monomer units(as the reacted form of monomers). The polymer or the molecule mixturetherefore in principle comprises molecules which comprise a plurality of(in other words, at least two) identical or different monomer units. Aproportion of the mixture may of course comprise the monomersthemselves, in other words in their unreacted form. This is a result, asis known, simply of the preparation reaction—i.e., polymerization ofmonomers—which in general does not proceed with molecular uniformity.While a particular monomer can be ascribed a discrete molecular weight,then, a polymer is always a mixture of molecules differing in theirmolecular weight. Consequently it is not possible to describe a polymerby a discrete molecular weight; instead, as is known, it is alwaysassigned average molecular weights, an example being the number-averagemolecular weight stated above.

In the polyether for use in accordance with the invention, all nradicals R may be the same. It is also possible, though, for differentkinds of radicals R to be present. Preferably all the radicals R are thesame.

R is preferably a C₄ alkylene radical. More preferably it is atetramethylene radical.

With very particular preference the polyether for use in accordance withthe invention is a linear polytetrahydrofuran which on average isdiolic.

The Reaction Product

There are no peculiarities to the preparation of the reaction product.The components (a) and (b) are linked with one another viacommon-knowledge reactions of condensation and/or addition of hydroxylgroups with carboxylic anhydrides and carboxylic acids. The reaction maytake place, for example, in bulk or in solution with typical organicsolvents at temperatures of 100° C. to 300° C., for example. Use may ofcourse also be made of typical catalysts such as sulfuric acid, sulfonicacids and/or tetraalkyl titanates, zinc and/or tin alkoxylates,dialkyltin oxides such as di-n-butyltin oxide, for example, or organicsalts of the dialkyltin oxides. At least in the case of condensationreactions, moreover, it is customary to use a water separator to collectthe water arising. It should of course be noted that acarboxy-functional reaction product is to form. Since component (b) isemployed in excess, care must be taken to ensure that the particulardesired amount of carboxyl groups remains in the resulting product. Thiscan readily be achieved by the skilled person by monitoring the acidnumber in the course of the reaction, by means of correspondingmeasurements, and terminating the reaction after the desired acid numberhas been reached, such termination being accomplished, for example, bycooling to a temperature at which reaction can no longer take place.

The components (a) and (b) here are used in a molar ratio of 0.7/2.3 to1.6/1.7, preferably of 0.8/2.2 to 1.6/1.8, and very preferably of0.9/2.1 to 1.5/1.8. A further particularly preferred ratio range is from0.45/1 to 0.55/1.

The reaction product is carboxy-functional. The acid number of thereaction product is from 5 to 50 mg KOH/g, preferably 8 to 40 mg KOH/g,especially preferably 10 to 35 mg KOH/g, and very preferably 12 to 30 mgKOH/g. The acid number is determined in accordance with DIN 53402 andrelates, of course, in each case to the product per se (and not to theacid number of any solution or dispersion of the product in a solventthat is present). Where reference is made to an official standard in thecontext of the present invention, the reference is of course to theversion of the standard applicable on filing or, if there is noapplicable version at that point in time, to the last applicableversion.

The resulting reaction product possesses preferably a number-averagemolecular weight of 1500 to 15 000 g/mol, preferably of 2000 to 10 000g/mol, and very preferably of 2200 to 8000 g/mol.

The reaction product of the invention is generally hydroxy-functional,preferably on average dihydroxy-functional. Hence with preference itpossesses not only hydroxyl functions but also carboxyl functions.

For especially preferred reaction products it is the case that they arepreparable by reaction of (a) trimellitic anhydride with (b) a diolic,linear polytetrahydrofuran having a number-average molecular weight of1500 to 3200 g/mol, the components (a) and (b) are used in a molar ratioof 0.45/1 to 0.55/1, and the reaction products have an acid number of 8to 40 mg KOH/g and a number-average molecular weight of 2000 to 10 000g/mol.

The Pigmented Aqueous Basecoat Material

The present invention relates further to a pigmented aqueous basecoatmaterial which comprises at least one reaction product of the invention.All of the above-stated preferred embodiments in relation to thereaction product also apply, of course, to the basecoat materialcomprising the reaction product.

A basecoat material is understood to be a color-imparting intermediatecoating material that is used in automotive finishing and generalindustrial painting. This basecoat material is generally applied to ametallic or plastics substrate which has been pretreated with a baked(fully cured) surfacer or primer-surfacer, or else, occasionally, isapplied directly to the plastics substrate. Substrates used may alsoinclude existing paint systems, which may optionally requirepretreatment as well (by abrading, for example). It has now becomeentirely customary to apply more than one basecoat film. Accordingly, insuch a case, a first basecoat film constitutes the substrate for asecond such film. A particular possibility in this context, instead ofapplication to a coat of a baked surfacer, is to apply the firstbasecoat material directly to a metal substrate provided with a curedelectrocoat, and to apply the second basecoat material directly to thefirst basecoat film, without separately curing the latter. To protect abasecoat film, or the uppermost basecoat film, from environmentaleffects in particular, at least an additional clearcoat film is appliedover it. This is generally done in a wet-on-wet process—that is, theclearcoat material is applied without the basecoat film(s) being cured.Curing then takes place, finally, jointly. It is now also widespreadpractice to produce only one basecoat film on a cured electrocoat film,then to apply a clearcoat material, and then to cure these two filmsjointly. The latter is a preferred embodiment in the context of thepresent invention. The reason is that when using the reaction product ofthe invention, in spite of the production of only one basecoat andtherefore of a consequent significant simplification in operation, theresult is excellent adhesion and also stonechip resistance.

The sum total of the weight-percentage fractions, based on the totalweight of the pigmented aqueous basecoat material, of all reactionproducts of the invention is preferably 0.1 to 20 wt %, more preferably0.5 to 15 wt %, and very preferably 1.0 to 10 wt % or even 1.5 to 5 wt%.

Where the amount of the reaction product of the invention is below 0.1wt %, it may be possible that no further improvement in adhesion andstonechip resistance is achieved. Where the amount is more than 20 wt %,there may in certain circumstances be disadvantages, on account of thethen numerous potentially anionic groups (carboxylate groups) in thereaction product, in terms of the condensation resistance of the paintsystem produced from the basecoat material.

In the case of a possible particularization to basecoat materialscomprising preferred reaction products in a specific proportional range,the following applies. The reaction products which do not fall withinthe preferred group may of course still be present in the basecoatmaterial. In that case the specific proportional range applies only tothe preferred group of reaction products. It is preferred nonethelessfor the total proportion of reaction products, consisting of reactionproducts of the preferred group and reaction products which are not partof the preferred group, to be subject likewise to the specificproportional range.

In the case of restriction to a proportional range of 0.5 to 15 wt % andto a preferred group of reaction products, therefore, this proportionalrange evidently applies initially only to the preferred group ofreaction products. In that case, however, it would be preferable forthere to be likewise from 0.5 to 15 wt % in total present of alloriginally encompassed reaction products, consisting of reactionproducts from the preferred group and reaction products which do notform part of the preferred group. If, therefore, 5 wt % of reactionproducts of the preferred group are used, not more than 10 wt % of thereaction products of the nonpreferred group may be used.

The stated principle is valid, for the purposes of the presentinvention, for all stated components of the basecoat material and fortheir proportional ranges—for example, for the pigments, for thepolyurethane resins as binders, or else for the crosslinking agents suchas melamine resins.

The basecoat materials used in accordance with the invention comprisecolor and/or effect pigments. Such color pigments and effect pigmentsare known to those skilled in the art and are described, for example, inRömpp-Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, NewYork, 1998, pages 176 and 451. The fraction of the pigments may besituated for example in the range from 1 to 40 wt %, preferably 2 to 35wt %, more preferably 3 to 30 wt %, based on the total weight of thepigmented aqueous basecoat material.

Preferred basecoat materials in the context of the present invention arethose which comprise, as binders, polymers curable physically,thermally, or both thermally and with actinic radiation. A “binder” inthe context of the present invention and in accordance with relevant DINEN ISO 4618 is the nonvolatile component of a coating composition,without pigments and fillers. Specific binders, accordingly, include,for example, typical coatings additives, the reaction product of theinvention, or typical crosslinking agents described later on below, evenif the expression is used primarily below in relation to particularpolymers curable physically, thermally, or both thermally and withactinic radiation, as for example particular polyurethane resins.

Besides the reaction product of the invention, the pigmented aqueousbasecoat materials of the invention more preferably comprise at leastone further polymer, different from the reaction product, as binder,more particularly at least one polymer selected from the groupconsisting of polyurethanes, polyesters, poly(meth)acrylates and/orcopolymers of the stated polymers, especially preferably at any rate,though not necessarily exclusively, at least onepolyurethane-poly(meth)acrylate.

In the context of the present invention, the term “physical curing”means the formation of a film through loss of solvent from polymersolutions or polymer dispersions. Typically, no crosslinking agents arenecessary for this curing.

In the context of the present invention, the term “thermal curing” meansthe heat-initiated crosslinking of a coating film, with either aseparate crosslinking agent or else self-crosslinking binders beingemployed in the parent coating material. The crosslinking agent containsreactive functional groups which are complementary to the reactivefunctional groups present in the binders. This is commonly referred toby those in the art as external crosslinking. Where the complementaryreactive functional groups or autoreactive functional groups—that is,groups which react with groups of the same kind—are already present inthe binder molecules, the binders present are self-crosslinking.Examples of suitable complementary reactive functional groups andautoreactive functional groups are known from German patent applicationDE 199 30 665 A1, page 7 line 28 to page 9 line 24.

For the purposes of the present invention, actinic radiation meanselectromagnetic radiation such as near infrared (NIR), UV radiation,more particularly UV radiation, and particulate radiation such aselectron radiation. Curing by UV radiation is commonly initiated byradical or cationic photoinitiators. Where thermal curing and curingwith actinic light are employed in unison, the term “dual cure” is alsoused.

In the present invention preference is given both to basecoat materialswhich are curable physically and to those which are curable thermally.In the case of basecoat materials which are curable thermally, there isof course always also a proportion of physical curing. For reasons notleast of ease of comprehension, however, these coating materials arereferred to as thermally curable.

Preferred thermally curing basecoat materials are those which compriseas binder a polyurethane resin and/or polyurethane-poly(meth)acrylate,preferably a hydroxyl-containing polyurethane resin and/orpolyurethane-poly(meth)acrylate, and as crosslinking agent an aminoplastresin or a blocked or nonblocked polyisocyanate, preferably anaminoplast resin. Among the aminoplast resins, melamine resins arepreferred.

The sum total of the weight-percentage fractions, based on the totalweight of the pigmented aqueous basecoat material, of all crosslinkingagents, preferably aminoplast resins and/or blocked and/or nonblockedpolyisocyanates, more particularly preferably melamine resins, ispreferably 1 to 20 wt %, more preferably 1.5 to 17.5 wt %, and verypreferably 2 to 15 wt % or even 2.5 to 10 wt %.

The polyurethane resin preferably present may be ionically and/ornonionically hydrophilically stabilized. In preferred embodiments of thepresent invention the polyurethane resin is ionically hydrophilicallystabilized. The preferred polyurethane resins are linear or containinstances of branching. The polyurethane resin is more preferably one inwhose presence olefinically unsaturated monomers have been polymerized.This polyurethane resin may be present alongside the polymer originatingfrom the polymerization of the olefinically unsaturated monomers,without these polymers being bonded covalently to one another. Equally,however, the polyurethane resin may also be bonded covalently to thepolymer originating from the polymerization of the olefinicallyunsaturated monomers. Both groups of the aforementioned resins, then,are copolymers, which in the case of the use of(meth)acrylate-group-containing monomers as olefinically unsaturatedmonomers, can also be called polyurethane-poly(meth)acrylates (see alsoearlier on above). This kind of polyurethane-poly(meth)acrylates, moreparticularly hydroxy-functional polyurethane-poly(meth)acrylates, areparticularly preferred for use in the context of the present invention.The olefinically unsaturated monomers are thus preferably monomerscontaining acrylate groups and/or methacrylate groups. It is likewisepreferred for the monomers containing acrylate and/or methacrylategroups to be used in combination with other olefinically unsaturatedcompounds which contain no acrylate or methacrylate groups. Olefinicallyunsaturated monomers bonded covalently to the polyurethane resin aremore preferably monomers containing acrylate groups or methacrylategroups. This form of polyurethane-poly(meth)acrylates is furtherpreferred.

Suitable saturated or unsaturated polyurethane resins and/orpolyurethane-poly(meth)acrylates are described, for example, in

German patent application DE 199 14 896 A1, column 1, lines 29 to 49 andcolumn 4, line 23 to column 11, line 5,

German patent application DE 199 48 004 A1, page 4, line 19 to page 13,line 48,

European patent application EP 0 228 003 A1, page 3, line 24 to page 5,line 40,

European patent application EP 0 634 431 A1, page 3, line 38 to page 8,line 9, or

international patent application WO 92/15405, page 2, line 35 to page10, line 32, or

German patent application DE 44 37 535 A1.

The polyurethane resin is prepared using preferably the aliphatic,cycloaliphatic, aliphatic-cycloaliphatic, aromatic, aliphatic-aromaticand/or cycloaliphatic-aromatic polyisocyanates that are known to theskilled person.

As alcohol component for preparing the polyurethane resins, preferenceis given to using the saturated and unsaturated polyols of relativelyhigh molecular mass and of low molecular mass, and also, optionally,monoalcohols, in minor amounts, that are known to the skilled person.Low molecular mass polyols used are more particularly diols and, inminor amounts, triols, for introducing instances of branching. Examplesof suitable polyols of relatively high molecular mass are saturated orolefinically unsaturated polyester polyols and/or polyether polyols.Relatively high molecular mass polyols are more particularly polyesterpolyols, especially those having a number-average molecular weight of400 to 5000 g/mol.

For hydrophilic stabilization and/or for increasing the dispersibilityin aqueous medium, the polyurethane resin preferably present may containparticular ionic groups and/or groups which can be converted into ionicgroups (potentially ionic groups). Polyurethane resins of this kind arereferred to in the context of the present invention as ionicallyhydrophilically stabilized polyurethane resins. Likewise present may benonionic hydrophilically modifying groups. Preferred, however, are theionically hydrophilically stabilized polyurethanes. In more preciseterms, the modifying groups are alternatively

-   -   functional groups which can be converted to cations by        neutralizing agents and/or quaternizing agents, and/or cationic        groups (cationic modification)

or

-   -   functional groups which can be converted to anions by        neutralizing agents, and/or anionic groups (anionic        modification)

and/or

-   -   nonionic hydrophilic groups (nonionic modification).

As the skilled person is aware, the functional groups for cationicmodification are, for example, primary, secondary and/or tertiary aminogroups, secondary sulfide groups and/or tertiary phosphine groups, moreparticularly tertiary amino groups and secondary sulfide groups(functional groups which can be converted to cationic groups byneutralizing agents and/or quaternizing agents). Mention should also bemade of the cationic groups—groups prepared from the aforementionedfunctional groups using neutralizing agents and/or quaternizing agentsknown to those skilled in the art—such as primary, secondary, tertiaryand/or quaternary ammonium groups, tertiary sulfonium groups and/orquaternary phosphonium groups, more particularly quaternary ammoniumgroups and tertiary sulfonium groups.

As is well known, the functional groups for anionic modification are,for example, carboxylic acid, sulfonic acid and/or phosphonic acidgroups, more particularly carboxylic acid groups (functional groupswhich can be converted to anionic groups by neutralizing agents), andalso anionic groups—groups prepared from the aforementioned functionalgroups using neutralizing agents known to the skilled person—such ascarboxylate, sulfonate and/or phosphonate groups.

The functional groups for nonionic hydrophilic modification arepreferably poly(oxyalkylene) groups, more particularly poly(oxyethylene)groups.

The ionically hydrophilic modifications can be introduced into thepolyurethane resin through monomers which contain the (potentially)ionic groups. The nonionic modifications are introduced, for example,through the incorporation of poly(ethylene) oxide polymers as lateral orterminal groups in the polyurethane molecules. The hydrophilicmodifications are introduced, for example, via compounds which containat least one group reactive toward isocyanate groups, preferably atleast one hydroxyl group. The ionic modification can be introduced usingmonomers which, as well as the modifying groups, contain at least onehydroxyl group. To introduce the nonionic modifications, preference isgiven to using the polyether diols and/or alkoxypoly(oxyalkylene)alcohols known to those skilled in the art.

As already indicated above, the polyurethane resin may preferably be agraft polymer by means of olefinically unsaturated monomers. In thiscase, then, the polyurethane is grafted, for example, with side groupsand/or side chains that are based on olefinically unsaturated monomers.These are more particularly side chains based on poly(meth)acrylates,with the systems in question then being thepolyurethane-poly(meth)acrylates already described above.Poly(meth)acrylates for the purposes of the present invention arepolymers or polymeric radicals which comprise monomers containingacrylate and/or methacrylate groups, and preferably consist of monomerscontaining acrylate groups and/or methacrylate groups. Side chains basedon poly(meth)acrylates are understood to be side chains which areconstructed during the graft polymerization, using monomers containing(meth)acrylate groups. In the graft polymerization, preference here isgiven to using more than 50 mol %, more particularly more than 75 mol %,especially 100 mol %, based on the total amount of the monomers used inthe graft polymerization, of monomers containing (meth)acrylate groups.

The side chains described are introduced into the polymer preferablyafter the preparation of a primary polyurethane resin dispersion (seealso description earlier on above). In this case the polyurethane resinpresent in the primary dispersion may contain lateral and/or terminalolefinically unsaturated groups via which, then, the graftpolymerization with the olefinically unsaturated compounds proceeds. Thepolyurethane resin for grafting may therefore be an unsaturatedpolyurethane resin. The graft polymerization is in that case a radicalpolymerization of olefinically unsaturated reactants. Also possible, forexample, is for the olefinically unsaturated compounds used for thegraft polymerization to contain at least one hydroxyl group. In thatcase it is also possible first for there to be attachment of theolefinically unsaturated compounds via these hydroxyl groups throughreaction with free isocyanate groups of the polyurethane resin. Thisattachment takes place instead of or in addition to the radical reactionof the olefinically unsaturated compounds with the lateral and/orterminal olefinically unsaturated groups optionally present in thepolyurethane resin. This is then followed again by the graftpolymerization via radical polymerization, as described earlier onabove. The result in any case is polyurethane resins grafted witholefinically unsaturated compounds, preferably olefinically unsaturatedmonomers.

As olefinically unsaturated compounds with which the polyurethane resinis preferably grafted it is possible to use virtually all radicallypolymerizable, olefinically unsaturated, and organic monomers which areavailable to the skilled person for these purposes. A number ofpreferred monomer classes may be specified by way of example:

hydroxyalkyl esters of (meth)acrylic acid or of otheralpha,beta-ethylenically unsaturated carboxylic acids,

(meth)acrylic acid alkyl and/or cycloalkyl esters having up to 20 carbonatoms in the alkyl radical,

ethylenically unsaturated monomers comprising at least one acid group,more particularly exactly one carboxyl group, such as (meth)acrylicacid, for example,

vinyl esters of monocarboxylic acids which are branched inalpha-position and have 5 to 18 carbon atoms,

reaction products of (meth)acrylic acid with the glycidyl ester of amonocarboxylic acid which is branched in alpha-position and has 5 to 18carbon atoms,

further ethylenically unsaturated monomers such as olefins (ethylene forexample), (meth)acrylamides, vinylaromatic hydrocarbons (styrene forexample), vinyl compounds such as vinyl chloride and/or vinyl etherssuch as ethyl vinyl ether.

Used with preference are monomers containing (meth)acrylate groups, andso the side chains attached by grafting are poly(meth)acrylate-basedside chains.

The lateral and/or terminal olefinically unsaturated groups in thepolyurethane resin, via which the graft polymerization with theolefinically unsaturated compounds can proceed, are introduced into thepolyurethane resin preferably via particular monomers. These particularmonomers, in addition to an olefinically unsaturated group, alsoinclude, for example, at least one group that is reactive towardisocyanate groups. Preferred are hydroxyl groups and also primary andsecondary amino groups. Especially preferred are hydroxyl groups.

The monomers described through which the lateral and/or terminalolefinically unsaturated groups may be introduced into the polyurethaneresin may also, of course, be employed without the polyurethane resinbeing additionally grafted thereafter with olefinically unsaturatedcompounds. It is preferred, however, for the polyurethane resin to begrafted with olefinically unsaturated compounds.

The polyurethane resin preferably present may be a self-crosslinkingand/or externally crosslinking binder. The polyurethane resin preferablycomprises reactive functional groups through which external crosslinkingis possible. In that case there is preferably at least one crosslinkingagent in the pigmented aqueous basecoat material. The reactivefunctional groups through which external crosslinking is possible aremore particularly hydroxyl groups. With particular advantage it ispossible, for the purposes of the method of the invention, to usepolyhydroxy-functional polyurethane resins. This means that thepolyurethane resin contains on average more than one hydroxyl group permolecule.

The polyurethane resin is prepared by the customary methods of polymerchemistry. This means, for example, the polymerization ofpolyisocyanates and polyols to polyurethanes, and the graftpolymerization that preferably then follows with olefinicallyunsaturated compounds. These methods are known to the skilled person andcan be adapted individually. Exemplary preparation processes andreaction conditions can be found in European patent EP 0521 928 B1, page2, line 57 to page 8, line 16.

The polyurethane resin preferably present possesses, for example, ahydroxyl number of 0 to 250 mg KOH/g, but more particularly from 20 to150 mg KOH/g. The acid number of the polyurethane resin is preferably 5to 200 mg KOH/g, more particularly 10 to 40 mg KOH/g. The hydroxylnumber is determined in the context of the present invention inaccordance with DIN 53240.

The polyurethane resin content is preferably between 5 and 80 wt %, morepreferably between 8 and 70 wt %, and more preferably between 10 and 60wt %, based in each case on the film-forming solids of the basecoatmaterial.

Irrespective of occasional reference in the context of the presentinvention both to polyurethanes (also called polyurethane resins) and topolyurethane-poly(meth)acrylates, the expression “polyurethanes”, as ageneric term, embraces the polyurethane-poly(meth)acrylates. If,therefore, no distinction is made between the two classes of polymer ina particular passage, but instead only the expression “polyurethane” or“polyurethane resin” is stated, both polymer classes are encompassed.

By film-forming solids, corresponding ultimately to the binder fraction,is meant the nonvolatile weight fraction of the basecoat material,without pigments and, where appropriate, fillers. The film-formingsolids can be determined as follows: A sample of the pigmented aqueousbasecoat material (approximately 1 g) is admixed with 50 to 100 timesthe amount of tetrahydrofuran and then stirred for around 10 minutes.The insoluble pigments and any fillers are then removed by filtrationand the residue is rinsed with a little THF, the THF being removed fromthe resulting filtrate on a rotary evaporator. The residue of thefiltrate is dried at 120° C. for two hours and the resultingfilm-forming solids are obtained by weighing.

The sum total of the weight-percentage fractions, based on the totalweight of the pigmented aqueous basecoat material, of all polyurethaneresins is preferably 2 to 40 wt %, more preferably 2.5 to 30 wt %, andvery preferably 3 to 25 wt %.

There is preferably also a thickener present. Suitable thickeners areinorganic thickeners from the group of the phyllosilicates. As well asthe inorganic thickeners, however, it is also possible to use one ormore organic thickeners. These are preferably selected from the groupconsisting of (meth)acrylic acid-(meth)acrylate copolymer thickeners, asfor example the commercial product Rheovis AS 5130 (BASF), and ofpolyurethane thickeners, as for example the commercial product RheovisPU 1250 (BASF). The thickeners used are different from the binders used.

Furthermore, the pigmented aqueous basecoat material may furthercomprise at least one adjuvant. Examples of such adjuvants are saltswhich can be decomposed thermally without residue or substantiallywithout residue, resins as binders that are curable physically,thermally and/or with actinic radiation and are different from theabove-described polymers, further crosslinking agents, organic solvents,reactive diluents, transparent pigments, fillers, molecularly disperselysoluble dyes, nanoparticles, light stabilizers, antioxidants, deaeratingagents, emulsifiers, slip additives, polymerization inhibitors,initiators of radical polymerizations, adhesion promoters, flow controlagents, film-forming assistants, sag control agents (SCAs), flameretardants, corrosion inhibitors, waxes, siccatives, biocides, andmatting agents. Also included may be thickeners such as organicthickeners from the group of the phyllosilicates or organic thickenerssuch as (meth)acrylic acid-(meth)acrylate copolymer thickeners, or elsepolyurethane thickeners, which are different from the binders used.

Suitable adjuvants of the aforementioned kind are known, for example,from

German patent application DE 199 48 004 A1, page 14, line 4, to page 17,line 5,

German patent DE 100 43 405 Cl column 5, paragraphs [0031] to [0033].

They are used in the customary and known amounts.

The solids content of the basecoat materials of the invention may varyaccording to the requirements of the case in hand. The solids content isguided primarily by the viscosity required for application, moreparticularly for spray application, and so may be adjusted by theskilled person on the basis of his or her general art knowledge,optionally with assistance from a few exploratory tests.

The solids content of the basecoat materials is preferably 5 to 70 wt %,more preferably 8 to 60 wt %, and very preferably 12 to 55 wt %.

By solids content (nonvolatile fraction) is meant that weight fractionwhich remains as a residue on evaporation under specified conditions. Inthe present application, the solids content, unless explicitly indicatedotherwise, is determined in accordance with DIN EN ISO 3251. This isdone by evaporating the basecoat material at 130° C. for 60 minutes.

Unless indicated otherwise, this test method is likewise employed inorder to determine, for example, the fraction of various components ofthe basecoat material as a proportion of the total weight of thebasecoat material. Thus, for example, the solids content of a dispersionof a polyurethane resin which is to be added to the basecoat materialmay be determined correspondingly in order to ascertain the fraction ofthis polyurethane resin as a proportion of the overall composition.

The basecoat material of the invention is aqueous. The expression“aqueous” is known in this context to the skilled person. The phraserefers in principle to a basecoat material which is not basedexclusively on organic solvents, i.e., does not contain exclusivelyorganic-based solvents as its solvents but instead, in contrast,includes a significant fraction of water as solvent. “Aqueous” for thepurposes of the present invention should preferably be understood tomean that the coating composition in question, more particularly thebasecoat material, has a water fraction of at least 40 wt %, preferablyat least 50 wt %, very preferably at least 60 wt %, based in each caseon the total amount of the solvents present (i.e., water and organicsolvents). Preferably in turn, the water fraction is 40 to 90 wt %, moreparticularly 50 to 80 wt %, very preferably 60 to 75 wt %, based in eachcase on the total amount of the solvents present.

The basecoat materials employed in accordance with the invention may beproduced using the mixing assemblies and mixing techniques that arecustomary and known for producing basecoat materials.

The Method of the Invention and the Multicoat Paint System of theInvention

A further aspect of the present invention is a method for producing amulticoat paint system, by

(1) applying a pigmented aqueous basecoat material to a substrate,

(2) forming a polymer film from the coating material applied in stage(1),

(3) applying a clearcoat material to the resultant basecoat, and then

(4) curing the basecoat together with the clearcoat,

which comprises using in stage (1) a pigmented aqueous basecoat materialwhich comprises at least one reaction product of the invention. All ofthe above observations relating to the reaction product of the inventionand to the pigmented aqueous basecoat material are also valid in respectof the method of the invention. This is true more particularly also ofall preferred, very preferred, and especially preferred features.

Said method is preferably used to produce multicoat color paint systems,effect paint systems, and color and effect paint systems.

The pigmented aqueous basecoat material used in accordance with theinvention is commonly applied to metallic or plastics substrates thathave been pretreated with surfacer or primer-surfacer. Said basecoatmaterial may optionally also be applied directly to the plasticssubstrate.

Where a metallic substrate is to be coated, it is preferably furthercoated with an electrocoat system before the surfacer or primer-surfaceris applied.

Where a plastics substrate is being coated, it is preferably alsopretreated before the surfacer or primer-surfacer is applied. Thetechniques most frequently employed for such pretreatment are those offlaming, plasma treatment, and corona discharge. Flaming is used withpreference.

Application of the pigmented aqueous basecoat material of the inventionto metallic substrates already coated, as described above, with curedelectrocoat systems and/or surfacers may take place in the filmthicknesses customary within the automobile industry, in the range, forexample, of 5 to 100 micrometers, preferably 5 to 60 micrometers (dryfilm thickness). This is done using spray application methods, as forexample compressed air spraying, airless spraying, high-speed rotation,electrostatic spray application (ESTA), alone or in conjunction with hotspray application, such as for example, hot air spraying.

Following the application of the pigmented aqueous basecoat material, itcan be dried by known methods. For example, (1-component) basecoatmaterials, which are preferred, can be flashed at room temperature for 1to 60 minutes and subsequently dried, preferably at optionally slightlyelevated temperatures of 30 to 90° C. Flashing and drying in the contextof the present invention mean the evaporation of organic solvents and/orwater, as a result of which the paint becomes drier but has not yetcured or not yet formed a fully crosslinked coating film.

Then a commercial clearcoat material is applied, by likewise commonmethods, the film thicknesses again being within the customary ranges,for example 5 to 100 micrometers (dry film thickness).

After the clearcoat material has been applied, it can be flashed at roomtemperature for 1 to 60 minutes, for example, and optionally dried. Theclearcoat material is then cured together with the applied pigmentedbasecoat material. In the course of these procedures, crosslinkingreactions occur, for example, to produce on a substrate a multicoatcolor and/or effect paint system of the invention. Curing takes placepreferably thermally at temperatures from 60 to 200° C. Thermally curingbasecoat materials are preferably those which comprise as additionalbinder a polyurethane resin and as crosslinking agent an aminoplastresin or a blocked or nonblocked polyisocyanate, preferably anaminoplast resin. Among the aminoplast resins, melamine resins arepreferred.

In one particular embodiment, the method for producing a multicoat paintsystem comprises the following steps:

producing a cured electrocoat film on the metallic substrate byelectrophoretic application of an electrocoat material to the substrateand subsequent curing of the electrocoat material,

producing (i) a basecoat film or (ii) a plurality of basecoat filmsdirectly following one another directly on the cured electrocoat film by(i) application of an aqueous basecoat material directly to theelectrocoat film, or (ii) directly successive application of two or morebasecoat materials to the electrocoat film,

producing a clearcoat film directly on (i) the basecoat film or (ii) theuppermost basecoat film, by application of a clearcoat material directlyto (i) one basecoat film or (ii) the uppermost basecoat film,

where (i) one basecoat material or (ii) at least one of the basecoatmaterials is a basecoat material of the invention,

joint curing of the basecoat film (i) or of the basecoat films (ii) andalso of the clearcoat film.

In the latter embodiment, then, in comparison to the above-describedstandard methods, there is no application and separate curing of acommonplace surfacer. Instead, all of the films applied to theelectrocoat film are cured jointly, thereby making the overall operationmuch more economical. Nevertheless, in this way, and particularlythrough the use of a basecoat material of the invention comprising areaction product of the invention, multicoat paint systems areconstructed which have outstanding mechanical stability and adhesion andhence are particularly technologically outstanding.

The application of a coating material directly to a substrate ordirectly to a previously produced coating film is understood as follows:The respective coating material is applied in such a way that thecoating film produced from it is disposed on the substrate (on the othercoating film) and is in direct contact with the substrate (with theother coating film). Between coating film and substrate (other coatingfilm), therefore, there is more particularly no other coat.

Without the detail “direct”, the applied coating film, while disposed onthe substrate (the other film), need not necessarily be present indirect contact. More particularly, further coats may be disposed betweenthem. In the context of the present invention, therefore, the followingis the case: In the absence of particularization as to “direct”, thereis evidently no restriction to “direct”.

Plastics substrates are coated basically in the same way as metallicsubstrates. Here, however, in general, curing takes place atsignificantly lower temperatures, of 30 to 90° C. Preference istherefore given to the use of two-component clearcoat materials.

The method of the invention can be used to paint metallic andnonmetallic substrates, more particularly plastics substrates,preferably automobile bodies or components thereof.

The method of the invention can be used further for dual finishing inOEM finishing. This means that a substrate which has been coated bymeans of the method of the invention is painted for a second time,likewise by means of the method of the invention.

The invention relates further to multicoat paint systems which areproducible by the method described above. These multicoat paint systemsare to be referred to below as multicoat paint systems of the invention.

All of the above observations relating to the reaction product of theinvention and to the pigmented aqueous basecoat material are also validin respect of said multicoat paint system and of the method of theinvention. This is also true especially of all the preferred, morepreferred and most preferred features.

The multicoat paint systems of the invention are preferably multicoatcolor paint systems, effect paint systems, and color and effect paintsystems.

A further aspect of the invention relates to the method of theinvention, wherein said substrate from stage (1) is a multicoat paintsystem having defects. This substrate/multicoat paint system, whichpossesses defects, is therefore an original finish, which is to berepaired or completely recoated.

The method of the invention is suitable accordingly for repairingdefects on multicoat paint systems. Film defects are generally faults onand in the coating, usually named according to their shape or theirappearance. The skilled person is aware of a host of possible kinds ofsuch film defects. They are described for example in Römpp-Lexikon Lackeand Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, page235, “Film defects”.

The multicoat paint systems produced by means of the method of theinvention may likewise have such defects. In one preferred embodiment ofthe method of the invention, therefore, the substrate from stage (1) isa multicoat paint system of the invention which exhibits defects.

These multicoat paint systems are produced preferably on automobilebodies or parts thereof, by means of the method of the invention,identified above, in the context of automotive OEM finishing. Where suchdefects occur directly after OEM finishing has taken place, they arerepaired immediately. The term “OEM automotive refinishing” is thereforealso used. Where only small defects require repair, only the “spot” isrepaired, and the entire body is not completely recoated (dual coating).The former process is called “spot repair”. The use of the method of theinvention for remedying defects on multicoat paint systems (originalfinishes) of the invention in OEM automotive refinishing, therefore, isparticularly preferred.

Where reference is made, in the context of the present invention, to theautomotive refinish segment, in other words when the repair of defectsis the topic, and the substrate specified is a multicoat paint systempossessing defects, this of course means that this substrate/multicoatpaint system with defects (original finish) is generally located on aplastic substrate or on a metallic substrate as described above.

So that the repaired site has no color difference from the rest of theoriginal finish, it is preferred for the aqueous basecoat material usedin stage (1) of the method of the invention for repairing defects to bethe same as that which was used to produce the substrate/multicoat paintsystem with defects (original finish).

The observations above concerning the reaction product of the inventionand the aqueous pigmented basecoat material therefore are also valid forthe use, under discussion, of the method of the invention for repairingdefects on a multicoat paint system. This is also true in particular ofall stated preferred, very preferred, and especially preferred features.It is additionally preferred for the multicoat paint systems of theinvention that are to be repaired to be multicoat color paint systems,effect paint systems, and color and effect paint systems.

The above-described defects on the multicoat paint system of theinvention can be repaired by means of the above-described method of theinvention. For this purpose, the surface to be repaired on the multicoatpaint system may initially be abraded. The abrading is preferablyperformed by partially sanding, or sanding off, only the basecoat andthe clearcoat, optionally only the clearcoat, from the original finish,but not sanding off the primer layer and surfacer layer that aregenerally situated beneath them. In this way, during the refinish, thereis no need in particular for renewed application of specialty primersand primer-surfacers. This form of abrading has become establishedespecially in the OEM automotive refinishing segment, since here, incontrast to refinishing in a workshop, generally speaking, defects occuronly in the basecoat and/or clearcoat region, but do not, in particular,occur in the region of the underlying surfacer and primer coats. Defectsin the latter coats are more likely to be encountered in the workshoprefinish sector. Examples include paint damage such as scratches, whichare produced, for example, by mechanical effects and which often extenddown to the substrate surface (metallic or plastic substrate).

After the abrading procedure, the pigmented aqueous basecoat material isapplied to the defect site in the original finish by spray application:for example, by pneumatic atomization. After the pigmented aqueousbasecoat material has been applied, it can be dried by known methods.For example, the basecoat material may be dried at room temperature for1 to 60 minutes and subsequently dried at optionally slightly elevatedtemperatures of 30 to 80° C. Flashing and drying for the purposes of thepresent invention means evaporation of organic solvents and/or water,whereby the coating material is as yet not fully cured. For the purposesof the present invention it is preferred for the basecoat material tocomprise a polyurethane resin as binder and an aminoplast resin,preferably a melamine resin, as crosslinking agent.

A commercial clearcoat material is subsequently applied, by techniquesthat are likewise commonplace. Following application of the clearcoatmaterial, it may be flashed off at room temperature for 1 to 60 minutes,for example, and optionally dried. The clearcoat material is then curedtogether with the applied pigmented basecoat material.

In the case of so-called low-temperature baking, curing takes placepreferably at temperatures of 20 to 90° C. Preference here is given tousing two-component clearcoat materials. If, as described above, apolyurethane resin is used as further binder and an aminoplast resin isused as crosslinking agent, there is only slight crosslinking by theaminoplast resin in the basecoat film at these temperatures. Here, inaddition to its function as a curing agent, the aminoplast resin alsoserves for plasticizing and may assist pigment wetting. Besides theaminoplast resins, nonblocked isocyanates may also be used. Depending onthe nature of the isocyanate used, they crosslink at temperatures fromas low as 20° C. Waterborne basecoat materials of this kind are then ofcourse generally formulated as two-component systems.

In the case of what is called high-temperature baking, curing isaccomplished preferably at temperatures of 130 to 150° C. Here bothone-component and two-component clearcoat materials are used. If, asdescribed above, a polyurethane resin is used as further binder and anaminoplast resin is used as crosslinking agent, there is crosslinking bythe aminoplast resin in the basecoat film at these temperatures.

A further aspect of the present invention is the use of the reactionproduct of the invention in pigmented aqueous basecoat materials forimproving the adhesion and the stonechip resistance of paint systemsproduced using the basecoat material.

The invention is illustrated below using examples.

EXAMPLES

Determination of the Number-Average Molecular Weight:

The number-average molecular weight was determined by means of vaporpressure osmosis. Measurement took place using a vapor pressureosmometer (model 10.00 from Knauer) on concentration series of the testcomponent in toluene at 50° C. with benzophenone as calibration compoundfor the determination of the experimental calibration constant of theinstrument used (according to E. Schröder, G. Müller, K.-F. Arndt,“Leitfaden der Polymercharakterisierung” [Principles of polymercharacterization], Academy-Verlag, Berlin, pp. 47 -54, 1982, where thecalibration compound used was in fact benzil).

Production of Inventive Reaction Products (IR) and Also of ReactionProducts Used for Comparison (CR):

IR1:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 138.8 g of trimellitic anhydride and2890 g of PolyTHF2000 (from BASF SE) with an OH number of 56 mg KOH/g(1.45 mol) were heated slowly to 180° C. and held at that temperature(OH number determination according to DIN 53240). The progress of thereaction was monitored via the determination of the acid number. When anacid number of 15 mg KOH/g was reached, the batch was cooled and dilutedwith 745 g of butyl glycol.

The solids content of the resin is 80.2% (measured at 130° C. for 1 h ina forced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight: 4500 g/mol

Viscosity (70% in butyl glycol): 3300 mPas (measured at 23° C. using aBrookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 750 s⁻¹).

IR2:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 327 g of trimellitic anhydride and3400 g of PolyTHF1000 (from BASF SE) with an OH number of 112 mg KOH/g(3.4 mol) were heated slowly to 180° C. and held at that temperature (OHnumber determination according to DIN 53240). The progress of thereaction was monitored via the determination of the acid number. When anacid number of 26 mg KOH/g was reached, the melt was cooled and dilutedwith 149 g of butyl glycol to a solids content of about 80%.

The solids content of the resin is 81.1% (measured at 130° C. for 1 h ina forced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight (vapor pressure osmosis): 2300 g/mol

Viscosity (original): 2760 mPas (measured at 23° C. using a BrookfieldCAP 2000+ rotary viscometer, spindle 3, shear rate: 1250 s⁻¹).

IR3:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 38.4 g of trimellitic anhydride and1160 g of Terathane2900® (from INVISTA, Wichita, Kansas, USA) with an OHnumber of 38.7 mg KOH/g (0.4 mol) were heated slowly to 180° C. and heldat that temperature (OH number determination according to DIN 53240).The progress of the reaction was monitored via the determination of theacid number. When an acid number of 15 mg KOH/g was reached, the meltwas cooled and diluted with butyl glycol to a solids content of about80%.

The solids content of the resin is 81.3% (measured at 130° C. for 1 h ina forced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight: (vapor pressure osmosis): 5400 g/mol

Viscosity (70% in butyl glycol): 4460 mPas (measured at 23° C. using aBrookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 750 s⁻¹).

CR1:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 288.2 g of trimellitic anhydride and1950 g of PolyTHF650 (from BASF SE) with an OH number of 172.6 mg KOH/g(3.0 mol) were heated to 80° C. (OH number determination according toDIN 53240). When a clear melt was obtained, it was heated slowly to 160°C. and held at that temperature. The progress of the reaction wasmonitored via the determination of the acid number. When an acid numberof 38 mg KOH/g was reached, cooling gave, at room temperature, a viscousresin.

The solids content of the resin is 100% (measured at 130° C. for 1 h ina forced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight (vapor pressure osmosis): 1300 g/mol

Viscosity 80% in butyl glycol: 1723 mPas (measured at 23° C. using aBrookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 1250s⁻¹).

CR2:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 288.2 g of trimellitic anhydride and1950 g of PolyTHF650 (from BASF SE) with an OH number of 172.6 mg KOH/g(3.0 mol) were heated to 80° C. (OH number determination according toDIN 53240). When a clear melt was obtained, it was heated slowly to 160°C. and held at that temperature. The progress of the reaction wasmonitored via the determination of the acid number. When an acid numberof 27 mg KOH/g was reached, the batch was diluted with butyl glycol to asolids content of about 80%.

The solids content of the resin is 78% (measured at 130° C. for 1 h in aforced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight (vapor pressure osmosis): 1500 g/mol

Viscosity: 6486 mPas (measured at 23° C. using a Brookfield CAP 2000+rotary viscometer, spindle 3, shear rate: 750 s⁻¹).

CR3:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 384.2 g of trimellitic anhydride and1000 g of PolyTHF250 (from BASF SE) with an OH number of 449 mg KOH/g(4.0 mol) were heated slowly to 180° C. (OH number determinationaccording to DIN 53240) and held at that temperature until the acidnumber was 32 mg KOH/g. Thereafter the melt was cooled and diluted withbutyl glycol to a solids content of about 80%.

The solids content of the resin is 76.4% (measured at 130° C. for 1 h ina forced air oven on a 1 g sample with addition of 1 ml of methyl ethylketone)

Number-average molecular weight (vapor pressure osmosis): 400 g/mol

Viscosity: 11 200 mPas (measured at 23° C. using a Brookfield CAP 2000+rotary viscometer, spindle 3, shear rate: 750 s⁻¹).

CR4:

In a 4 l stainless steel reactor equipped with anchor stirrer,thermometer, condenser, thermometer for overhead temperaturemeasurement, and water separator, 384.2 g of trimellitic anhydride and1000 g of PolyTHF250 (from BASF SE) with an OH number of 449 mg KOH/g(4.0 mol) were heated slowly to 180° C. (OH number determinationaccording to DIN 53240) and held at that temperature until the acidnumber was 80 mg KOH/g. Thereafter the melt was cooled and diluted withbutyl glycol to a solids content of about 80%.

The solids content of the resin is 83.30% (measured at 130° C. for 1 hin a forced air oven on a 1 g sample with addition of 1 ml of methylethyl ketone)

Number-average molecular weight (vapor pressure osmosis): 300 g/mol

Viscosity (original): 2840 mPas (measured at 23° C. using a BrookfieldCAP 2000+ rotary viscometer, spindle 3, shear rate: 750 s⁻¹).

Preparation of Aqueous Basecoat Materials

The following should be taken into account regarding formulationconstituents and amounts thereof as indicated in the tables hereinafter.When reference is made to a commercial product or to a preparationprotocol described elsewhere, the reference, independently of theprincipal designation selected for the constituent in question, is toprecisely this commercial product or precisely the product prepared withthe referenced protocol.

Accordingly, where a formulation constituent possesses the principaldesignation “melamine-formaldehyde resin” and where a commercial productis indicated for this constituent, the melamine-formaldehyde resin isused in the form of precisely this commercial product. Any furtherconstituents present in the commercial product, such as solvents, musttherefore be taken into account if conclusions are to be drawn about theamount of the active substance (of the melamine-formaldehyde resin).

If, therefore, reference is made to a preparation protocol for aformulation constituent, and if such preparation results, for example,in a polymer dispersion having a defined solids content, then preciselythis dispersion is used. The overriding factor is not whether theprincipal designation that has been selected is the term “polymerdispersion” or merely the active substance, as for example “polymer”,“polyester” or “polyurethane-modified polyacrylate”. This must be takeninto account if conclusions are to be drawn concerning the amount of theactive substance (of the polymer).

All proportions indicated in the tables are parts by weight.

Preparation of a Non-Inventive Waterborne Basecoat Material 1

The components listed under “Aqueous phase” in table A were stirredtogether in the order stated to form an aqueous mixture. In the nextstep, an organic mixture was prepared from the components listed under“Organic phase”. The organic mixture was added to the aqueous mixture.The combined mixtures were then stirred for 10 minutes by usingdeionized water and dimethylethanolamine to a pH of 8 and to a sprayviscosity of 58 mPas under a shearing load of 1000 s⁻¹, measured using arotational viscometer (Rheomat RM 180 instrument from Mettler-Toledo) at23° C.

TABLE A Waterborne basecoat material 1 Component Parts by weight Aqueousphase Aqueous solution of 3% sodium 27 lithium magnesium phyllosilicateLaponite ® RD (from Altana-Byk) and 3% Pluriol ® P900 (from BASF SE)Deionized water 15.9 Butyl glycol (from BASF SE) 3.5 Hydroxy-functional,polyurethane- 2.4 modified polyacrylate; prepared as per page 7, line 55to page 8, line 23 of DE 4437535 A1 50 wt % strength solution of 0.2Rheovis ® PU 1250 (BASF SE) in butyl glycol, rheological agentHydroxy-functional polyester; 2.5 prepared as per example D, column 16,lines 37-59 of DE-A-4009858 TMDD 50% BG (from BASF SE), 52% 1.2 strengthsolution of 2,4,7,9- tetramethy1-5-decyne-4-7-diol in butyl glycolLuwipal ® 052 (from BASF SE), 4.7 melamine-formaldehyde resin 10%strength solution of N,N- 0.5 dimethylethanolamine (from BASF SE) inwater Polyurethane-based graft copolymer; 19.6 prepared in analogy to DE19948004 A1 (page 27 - example 2) Isopropanol (from BASF SE) 1.4Byk-347 ® (from Altana-Byk) 0.5 Pluriol ® P900 (from BASF SE) 0.3Tinuvin ® 384-2 (from BASF SE) 0.6 Tinuvin ® 123 (from BASF SE) 0.3Carbon black paste 4.3 Blue paste 11.4 Mica slurry 2.8 Organic phaseAluminum pigment (from Altana- 0.3 Eckart) Butyl glycol (from BASF SE)0.3 Polyurethane-based graft copolymer; 0.3 prepared in analogy to DE19948004 A1 (page 27 - example 2)

Preparation of Blue Paste:

The blue paste was prepared in 69.8 parts by weight of an acrylatedpolyurethane dispersion prepared as per international patent applicationWO 91/15528, binder dispersion A, 12.5 parts by weight of Paliogen® BlueL 6482, 1.5 parts by weight of dimethylethanolamine (10% strength in DIwater), 1.2 parts by weight of a commercial polyether (Pluriol® P900from BASF SE), and 15 parts by weight of deionized water.

Preparation of Carbon Black:

The carbon black was prepared in 25 parts by weight of an acrylatedpolyurethane dispersion prepared as per international patent applicationWO 91/15528, binder dispersion A, 10 parts by weight of carbon black,0.1 part by weight of methyl isobutyl ketone, 1.36 parts by weight ofdimethylethanolamine (10% strength in DI water), 2 parts by weight of acommercial polyether (Pluriol® P900 from BASF SE), and 61.45 parts byweight of deionized water.

Preparation of the Mica Slurry:

The mica slurry was obtained by using a stirring element to mix 1.5parts by weight of polyurethane-based graft copolymer, prepared in ananalogy to DE 19948004 A1 (page 27—example 2), and 1.3 parts by weightof the commercial Mica Mearlin Ext. Fine Violet 539V from Merck.

Preparation of a Noninventive Waterborne Basecoat Material 2

The basecoat material 2 was prepared in analogy to table A, but usingthe reaction product CR1 in place of the polyester prepared as perexample D, column 16, lines 37-59 of DE-A-4009858. The proportion usedof the reaction product CR1 was the same, through compensation of theamount of solvent and/or consideration of the solids content of thecomponent to be added.

Preparation of the Noninventive Waterborne Basecoat Materials 3 to 5 andof the Inventive Waterborne Basecoat Materials I1 to I3

In analogy to the preparation of the waterborne basecoat material 2,further basecoat materials were prepared by replacing the polyesterprepared as per example D, column 16, lines 37-59 of DE-A-4009858. Theproportion used of the reaction product CR1 was the same, throughcompensation of the amount of solvent and/or consideration of the solidscontent of the component to be added. Table B shows an overview of allthe basecoat materials.

TABLE B basecoat materials Reaction product Waterborne basecoat material1 Polyester as per DE-A-4009858 Waterborne basecoat material 2 CR1Waterborne basecoat material 3 CR2 Waterborne basecoat material 4 CR3Waterborne basecoat material 5 CR4 Waterborne basecoat material I1 IR1Waterborne basecoat material I2 IR2 Waterborne basecoat material I3 IR3

Comparison Between Waterborne Basecoat Materials 1-5 and I1-I3

Stonechip Resistance:

For the determination of the stonechip resistance, the multicoat paintsystems were produced according to the following general protocol:

The substrate used was a steel panel with dimensions of 10×20 cm, coatedwith a cathodic e-coat (cathodic electrocoat).

Applied to this panel first of all was the respective basecoat material(table B), applied pneumatically in a target film thickness (dry filmthickness) at 20 micrometers. After the basecoat had been flashed atroom temperature for 1 minute, it was subjected to interim drying in aforced air oven at 70° C. for 10 minutes. Over the interim-driedwaterborne basecoat, a customary two-component clearcoat material(Progloss® 372 from BASF Coatings GmbH) was applied in a target filmthickness (dry film thickness) at 40 micrometers. The resultingclearcoat was flashed at room temperature for 20 minutes. The waterbornebasecoat and the clearcoat were subsequently cured in a forced air ovenat 160° C. for 30 minutes.

The resulting multicoat paint systems were tested for their stonechipresistance. This was done using the stonechip test of DIN 55966-1. Theresults of the stonechip test were assessed in accordance with DIN ENISO 20567-1. Lower values represent better stonechip resistance.

The results are found in table 1. The waterborne basecoat material (WBM)detail indicates which WBM was used in the particular multicoat paintsystem.

TABLE 1 Stonechip resistance of waterborne basecoat materials 1-5 andI1-I3 WBM Stonechip outcome 1 2.5 2 2.5 3 2.0 4 3.5 5 4.0 I1 1.0 I2 1.5I3 1.0

The results emphasize that the use of the inventive reaction products inbasecoat materials significantly increases the stonechip resistance bycomparison with the waterborne basecoat materials 1-5. The best resultsare exhibited by reaction products IR1 and IR3.

Adhesion:

For the determination of the adhesion properties, the stability towardincidence of blisters and swelling after condensation storage wasinvestigated.

In this case, multicoat paint systems were produced according to thefollowing general protocol:

The substrate used was a steel panel with dimensions of 10×20 cm, coatedwith a standard cathodic e-coat (Cathoguard® 800 from BASF CoatingsGmbH).

The respective aqueous basecoat material as per table B was thenapplied, application taking place pneumatically in a target filmthickness (dry film thickness) at 20 micrometers. The resultingwaterborne basecoat was flashed at room temperature for 2 minutes andthen subjected to interim drying in a forced air oven at 70° C. for 10minutes. Over the interim-dried waterborne basecoat, a customarytwo-component clearcoat material (Progloss® 372 from BASF Coatings GmbH)was applied in a target film thickness (dry film thickness) at 40micrometers. The resulting clearcoat was flashed at room temperature for20 minutes. The waterborne basecoat and the clearcoat were subsequentlycured in a forced air oven at 140° C. for 20 minutes. The presentconstruction is referred to hereinafter as original finish.

In order to generate or simulate defects, this original finish is sandedwith abrasive paper and then subjected as described below to a newcomplete finish with basecoat and clearcoat. In this way, a dual paintsystem as part of OEM automotive refinishing is simulated.

First of all the respective aqueous basecoat material as per table B isapplied to the abraded original finish, application taking placepneumatically in a target film thickness (dry film thickness) at 20micrometers. The resulting waterborne basecoat was flashed at roomtemperature for 2 minutes and then subjected to interim drying in aforced air oven at 70° C. for 10 minutes. Applied over the interim-driedwaterborne basecoat was an 80° C. two-component clearcoat material(two-component refinished clearcoat, scratch-resistant, from BASFCoatings GmbH) in a target film thickness (dry film thickness) at 40micrometers. The resulting clearcoat was flashed at room temperature for20 minutes. The waterborne basecoat and the clearcoat were subsequentlycured in a forced air oven at 80° C. for 30 minutes.

The steel panels and refinish systems treated accordingly were thenstored over a period of 10 days in a conditioning chamber under CHconditions according to DIN EN ISO 6270-2:2005-09. 24 hours afterremoval from the conditioning chamber, the panels were then inspectedfor blistering and swelling.

The incidence of blisters was assessed as follows through a combinationof 2 values:

-   -   the number of blisters was evaluated by a quantity figure from 1        to 5, with ml denoting very few and m5 very many blisters.    -   The size of the blisters was evaluated by a size figure likewise        from 1 to 5, with gl denoting very small and g5 very large        blisters.    -   The designation m0g0 denotes, accordingly, a blister-free paint        system after condensation storage, and represents an outstanding        result in terms of blistering.

The results are found in table 2.

TABLE 2 Blistering and swelling of waterborne basecoat materials 1-5 andwaterborne basecoat materials 11-13 WBM Blistering Swelling 1 m5g4 none2 m5g3 severe 3 m3g2 slight 4 m5g3 severe 5 m5g5 very severe I1 m0g0none I2 m0g0 very slight I3 m0g0 none

The results emphasize that the use of the inventive reaction products inbasecoat materials significantly increases the adhesion in a refinishsystem in comparison to waterborne basecoat materials 1-5. The bestresults are shown in turn by reaction products IRl and IR3.

What is claimed is:
 1. A pigmented aqueous basecoat material, comprisinga polyether-based reaction product prepared by reacting (a) at least onecyclic carboxylic anhydride comprising a free carboxylic acid groupand/or a halide of a carboxylic acid group with (b) at least onepolyether of formula (I)

wherein R is a C₃ to C₆ alkylene radical and n is selected accordinglysuch that the polyether (b) possesses a number-average molecular weightof from 1000 to 4000 g/mol, a molar ratio of (a) to (b) ranges from0.7/2.3 to 1.6/1.7, the polyether-based reaction product has an acidnumber of 5 to 50 mg KOH/g, and a sum total of weight-percentagefractions, based on a total weight of the basecoat material, of allpolyether-based reaction products is 0.1 to 5.0 wt %.